I also have to add to this. I had been creating social networks for my clients. And, one of my clients was a doctor -- he was being harassed as the actual site owner for copyright infringement.
I knew I hadn't infringed on anyone's rights. But, Getty Images was still pursuing legal matters. They pointed out a photo posted by a member on the site. I noticed that this notice first came to us just a few hours after this member joined the site.
I also looked into the phone numbers and IP addresses of the person who posted it. Many years later, I don't remember how I connected the dots. But, it turns out someone from Getty Images had signed up for the site, posted the photo and tried to leverage it as digital extortion, basically.
We ignored them for months. But, the doctor started threatening to sue me. When, I knew I did nothing wrong. So, I took screenshots and let them know that I knew -- as well as proof that I had deleted that image and banned the member months prior (I always had my case prepared -- "just in case").
The harassment stopped (and, yes, it was GI not someone posing as them to scam us out of money. I let them know that I was a member of the media and that if their extortion didn't stop, I would post all of it.
BOTTOM LINE: Even when hosting a blog or anything else -- we still need to be careful. Just because we didn't post it, it doesn't mean we aren't liable. It's still on our sites. And, sometimes the most malicious characters are those that have already preplanned to come after you -- assuming you knew no better. So, it's definitely best to arm yourself with the law, knowledge and disclaimer. But, like the author says -- you still can be held accountable.